Your one-rep max — the most weight you can lift for a single perfect repetition — is the reference point around which nearly every strength program is built. You do not have to grind out a true max attempt to estimate it. The Epley formula (named after the strength coach who popularized it) converts a submaximal set — a weight you lifted for several reps — into a reliable estimate of that top-end single. This Epley calculator does the math instantly, shows how the Brzycki formula compares, and turns your estimated 1RM into practical 80%, 90% and 95% training loads you can actually use on the platform.
How to Use
- Enter the Weight Lifted — the total load on the bar, barbell plus plates, for the set you want to analyze.
- Type the Reps Completed — the clean, full-range repetitions you finished before you could not do another. Stop the count at the reps you completed with good form, not the reps you ground out with a half-range squat or a bounced bench.
- Pick the Exercise — Bench Press, Back Squat, Deadlift, Overhead Press or Barbell Row. The 1RM math is identical across lifts; the label simply keeps your results organized.
- Choose your Units — pounds or kilograms. The formula is unit-agnostic, so every result carries the unit you selected.
- Read the result card. The highlighted Epley Estimated 1RM is your headline number; the Brzycki estimate and the Epley-minus-Brzycki gap show how much the two peer formulas agree; the 80%, 90% and 95% loads are the weights you should actually train with.
For the cleanest estimate, use a set in the 3-to-8 rep range. Below 3 reps the formula barely moves the number; above 10 reps fatigue and technique break down and the estimate drifts upward.
The Epley Formula
The Epley equation is deliberately simple:
1RM = w × (1 + r / 30)
Where w is the weight lifted and r is the number of repetitions completed. Each extra rep adds 1/30th of the load to your estimated max. On a 225 lb set for 5 reps: 225 × (1 + 5/30) = 225 × 1.1667 = 262.5 lb. That is the number the result card highlights.
The companion Brzycki formula uses a different regression curve: 1RM = w × 36 / (37 − r). On the same 225 lb, 5-rep set it returns about 253.1 lb — roughly 9 lb lower. Epley tends to estimate a touch higher when reps climb, while Brzycki is more conservative. The gap between them is shown on the card so you can see how much uncertainty sits in the estimate rather than treating a single decimal as gospel.
Turning Your 1RM Into Training Loads
A 1RM by itself is not a workout. The percentage loads are where it becomes useful:
- 80% of 1RM — the hypertrophy range. Sets of 6 to 10 reps at this weight build muscle and work for most of your weekly volume.
- 90% of 1RM — the strength range. Sets of 2 to 4 reps here drive absolute strength gains without needing daily max attempts.
- 95% of 1RM — the peaking range. Single reps or doubles, used sparingly in the final weeks before a test or meet.
For a 262.5 lb Epley max, those loads are 210 lb, 236.25 lb and 249.38 lb respectively. If your program says "bench at 80% for 4 sets of 6," you now know exactly which plates to load.
Examples
Example 1 — A standard bench set. You bench 225 lb for 5 clean reps. The Epley estimate is 262.5 lb, Brzycki is 253.1 lb, and your 80% training load is 210 lb. If your next block prescribes 4 sets of 6 at 80%, load 210 lb rather than guessing from your ego.
Example 2 — A heavy triple. You deadlift 315 lb for 3 reps. Epley estimates 346.5 lb (315 × 1.10), Brzycki lands near 333.5 lb, and the 90% strength load is 311.85 lb. Notice the gap is only about 13 lb — at low rep counts the two formulas broadly agree.
Example 3 — A higher-rep back-off set. You press 185 lb overhead for 8 reps. Epley estimates 234.3 lb, Brzycki about 229.7 lb, and the gap widens slightly. This is exactly why coaches recommend estimating from a set near 5 reps rather than a set of 15.
Example 4 — Stress magnitude. Even when the input is enormous — a synthetic 1,000,000 lb "lift" for 5 reps — the engine returns 1,166,666.67 lb without overflow or rounding error, so the page stays stable at any input magnitude.
FAQ
What is the Epley formula?
The Epley formula estimates your one-rep max from a submaximal set: 1RM = weight × (1 + reps / 30). Each repetition adds 1/30 of the lifted weight to your projected max. It is one of the most widely used 1RM regression equations in strength coaching and weightlifting research.
How accurate is the Epley calculator?
It is an estimate, not a measurement. Validation studies show Epley and Brzycki estimates typically land within 3–5% of a lab-tested 1RM when the input set is between 3 and 8 reps. Accuracy drops if you count sloppy reps, if the set is very low (1–2 reps) or very high (10+ reps), or if you are de-trained or peaking.
Should I use Epley or Brzycki?
They are both peer-reviewed regressions and usually agree within a few pounds. Epley estimates slightly higher as reps climb; Brzycki is more conservative. Many coaches average the two or simply pick one and stay consistent so progress tracking is comparable week to week. This calculator shows both side by side.
What percentage of my 1RM should I train with?
Most strength programs build volume at around 70–80% of 1RM for 6–10 reps, strength at 85–90% for 2–5 reps, and peak single reps near 95%. The 80%, 90% and 95% rows on this result card give you those loads directly so you do not have to do the multiplication mid-workout.
Can I use Epley for squats, deadlifts and overhead press?
Yes. The equation is lift-agnostic; it only needs a weight and a rep count. Select the exercise on the form to label the result. Be aware that technique and fatigue differ across lifts — a set of 8 on a deadlift is a worse input than a set of 5 because form breaks down faster under axial load.
What if I enter a negative number of reps?
The calculator rejects negative inputs: reps must be zero or positive, and the lifted weight must be non-negative. Entering a negative rep count returns an error rather than a nonsense estimate. A set of zero reps is treated as a degenerate boundary and simply returns the lifted weight itself.
Disclaimer
This Epley calculator is provided for informational purposes only and is not medical advice. Estimated one-rep maxima are statistical projections derived from submaximal sets and should not be used as a reason to attempt a true 1RM without proper warm-up, coaching, and a safe setup. Lifting near your maximum carries a real risk of injury; progress gradually, use good form, and consult a qualified strength coach or physician before beginning any new high-intensity program.